The present invention relates generally to container blanks and more particularly to a blank for a disposable thermally insulated container such as a paper cup.
Disposable paper cups with heat insulating capability are a desirable and widely used commodity. These types of cups are designed for hot liquid contents such as hot coffee/tea/chocolate and tend to maintain the liquid contents"" temperature by preventing undesirable heat transfer from the hot liquid contents inside the cup to the cup holder""s hand holding the cup. These cups may also be used for cold liquid contents in which case the insulated walls of the cup help maintain the cold liquid contents"" temperature by preventing undesirable heat transfer from the cup holder""s hand to the cold liquid contents.
Thermally insulated cups come in various known configurations. For example, an insulated cup is disclosed in Amberg et al (U.S. Pat. No. 3,737,093) which uses a plastic cup placed within a paper cup to create air space therebetween for thermal insulation purposes. Another insulated cup is disclosed by Iioka (U.S. Pat. No. 4,435,344) which coats a paper cup with a thermoplastic synthetic resin film which is subsequently heated to form a foamed insulating layer. Neale et al (U.S. Pat. No. 5,952,068) deals with a cup insulation layer formed from syntactic foam, a type of foam which incorporates insulating particles held in place by a binder. The insulating particles may contain an air space.
None of the known insulated cups, however, is an effective thermal insulator. Furthermore, none of the known insulated cups can be manufactured at low cost on a wide scale due to complexity of fabrication, high cost of materials, and the like.
The present invention is generally directed to a container blank comprising at least one substrate layer made of disposable material and at least one film layer disposed substantially over the substrate layer and having at least one portion adapted to shrink away from the substrate layer upon application of heat. The shrunk film layer portion is adapted to thermally insulate the substrate layer located substantially behind the shrunk film layer portion.
These and other aspects of the present invention will become apparent from a review of the accompanying drawings and the following detailed description of the preferred embodiments of the present invention.